WO2007109316A2 - Mécanisme de verrouillage cervical à rivet aveugle - Google Patents

Mécanisme de verrouillage cervical à rivet aveugle Download PDF

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Publication number
WO2007109316A2
WO2007109316A2 PCT/US2007/007014 US2007007014W WO2007109316A2 WO 2007109316 A2 WO2007109316 A2 WO 2007109316A2 US 2007007014 W US2007007014 W US 2007007014W WO 2007109316 A2 WO2007109316 A2 WO 2007109316A2
Authority
WO
WIPO (PCT)
Prior art keywords
pull
lock pin
section
diameter
bore
Prior art date
Application number
PCT/US2007/007014
Other languages
English (en)
Other versions
WO2007109316A3 (fr
Inventor
David T. Hawkes
Original Assignee
Alphaspine, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alphaspine, Inc. filed Critical Alphaspine, Inc.
Publication of WO2007109316A2 publication Critical patent/WO2007109316A2/fr
Publication of WO2007109316A3 publication Critical patent/WO2007109316A3/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
    • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
    • A61B17/88—Osteosynthesis instruments; Methods or means for implanting or extracting internal or external fixation devices
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
    • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
    • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
    • A61B17/80—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates
    • A61B17/8033—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates having indirect contact with screw heads, or having contact with screw heads maintained with the aid of additional components, e.g. nuts, wedges or head covers
    • A61B17/8038—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates having indirect contact with screw heads, or having contact with screw heads maintained with the aid of additional components, e.g. nuts, wedges or head covers the additional component being inserted in the screw head
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
    • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
    • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
    • A61B17/70—Spinal positioners or stabilisers ; Bone stabilisers comprising fluid filler in an implant
    • A61B17/7059—Cortical plates
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
    • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
    • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
    • A61B17/80—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
    • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
    • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
    • A61B17/80—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates
    • A61B17/8033—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates having indirect contact with screw heads, or having contact with screw heads maintained with the aid of additional components, e.g. nuts, wedges or head covers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
    • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
    • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
    • A61B17/80—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates
    • A61B17/8033—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates having indirect contact with screw heads, or having contact with screw heads maintained with the aid of additional components, e.g. nuts, wedges or head covers
    • A61B17/8047—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates having indirect contact with screw heads, or having contact with screw heads maintained with the aid of additional components, e.g. nuts, wedges or head covers wherein the additional element surrounds the screw head in the plate hole
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
    • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
    • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
    • A61B17/80—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates
    • A61B17/8052—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates immobilised relative to screws by interlocking form of the heads and plate holes, e.g. conical or threaded
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
    • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
    • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
    • A61B17/84—Fasteners therefor or fasteners being internal fixation devices
    • A61B17/86—Pins or screws or threaded wires; nuts therefor
    • A61B17/8685—Pins or screws or threaded wires; nuts therefor comprising multiple separate parts
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/03—Automatic limiting or abutting means, e.g. for safety
    • A61B2090/037—Automatic limiting or abutting means, e.g. for safety with a frangible part, e.g. by reduced diameter

Definitions

  • the present system and method relate to bone fixation devices. More particularly, the present system and method provide for an orthopedic system including a plate, a screw system, and a screw securing system including a pop-rivet locking mechanism.
  • the plate be reasonably congruent with the bone to which it is applied, that it have as low a profile as possible, that it be firmly secured to the spinal column so that it is not torn out when the patient places weight and stress upon it and that it be capable of placement and fixation in a manner that is convenient for the surgeon.
  • the plate In this context it is necessary to secure the plate to the spinal body and also, in some cases, to the graft. Conventionally, such attachment would be by the use of screws driven through screw holes in the plate into the bone.
  • the plate when stabilizing the position of cervical vertebrae, the plate is designed to lie near and posterior to the esophagus of the patient. Due to its relative location to the esophagus and other connective tissue, if the screw securing the plate to the cervical spine backs out, the screw could irritate or even pierce the esophagus, resulting in pain, infection, and/or possible death of the patient. Consequently, anti-back out mechanisms are desired in the orthopedic plate industry.
  • an orthopedic bone fixation device for stabilizing a plurality of bone segments includes a bone plate and a screw assembly.
  • the bone plate includes a body defining at least one thru-bore, wherein the thru-bore is defined to include a central cavity, the central cavity having a middle diameter, an entry diameter, and an exit diameter, the middle diameter being larger than both the entry diameter and the exit diameter.
  • the screw assembly is configured to be coupled to the bone plate, wherein the screw assembly includes a bone screw having a head section, a thread section, and a central bore, an expandable ring coupled to the head section, and a pin at least partially disposed in the central bore, wherein the pin includes a varying outer profile that engages the expandable ring to vary an outer diameter of the expandable ring to lock the screw assembly in the thru-bore.
  • the pin is configured to be pulled out from the central bore to engage an increasing diameter with the expandable ring. The frictional force exerted by the increasing diameter of the pin is increased as the pin is pulled from the bore, until the frictional force resists a pull force greater than a yield or fracture force of the pin. Upon fracture of the pin, the force exerting diameter remains acting upon the ring, while eliminating protrusions from the top of the assembly.
  • FIG. 1 is a side view of an assembled cervical plate system, according to one exemplary embodiment.
  • FIG. 2 is an exploded view illustrating the components of the screw assembly and bone plate of the exemplary embodiment illustrated in FIG. 1.
  • FIGS. 3A-3C are respectively top, side, and cross-sectional views of a bone plate, according to various exemplary embodiments.
  • FIGS. 4A-4D are respectively a side, a bottom, a top, and a cross-sectional view of a bone screw, according to one exemplary embodiment.
  • FIGS. 5A and 5B are respectively a top and a side view of an expandable ring configured to be mated with a bone screw, according to one exemplary embodiment.
  • FIG. 6 is a side view of a pull-lock pin, according to one exemplary embodiment.
  • FIG. 7 is a flow chart illustrating a method of securing an orthopedic plate, according to one exemplary embodiment.
  • FIG. 8 is an enlarged cross-sectional view of a thru-bore of an orthopedic plate during installation, according to one exemplary embodiment.
  • FIGS. 9A and B are a perspective and a cross-sectional view, respectively, illustrating a screw system being inserted into a thru-bore of an orthopedic plate, according to one exemplary embodiment.
  • FIGS. 10A and B are a perspective and a cross-sectional view, respectively, showing a properly positioned screw system in a thru-bore of an orthopedic plate, in accordance with one exemplary embodiment.
  • FIG. 11 A and B are a perspective and a cross-sectional view, respectively, illustrating the removal of a fracturing pull pin, according to one exemplary embodiment.
  • FIG. 12A and B are a perspective and a cross-sectional view, respectively, illustrating enlarged cross-sectional view of a screw system securely coupled to a thru-bore of an orthopedic plate, according to one exemplary embodiment.
  • the present specification describes a system and a method for coupling an orthopedic plate to one or more bones while preventing back- out of the fastener. Further, according to one exemplary embodiment, the present specification describes the structure of an orthopedic plate system that prevents back-out of a screw while positionally fixing bone segments.
  • pin is used in conjunction with a split ring or other expandable ring. The pin is configured to be pulled out from a central bore of a screw to engage an increasing diameter with the expandable ring. The frictional force exerted by the increasing diameter of the pin is increased as the pin is pulled from the bore, until the frictional force resists a pull force greater than a yield or fracture force of the pin. Upon fracture of the pin, the force exerting diameter remains acting upon the ring, while eliminating protrusions from the top of the assembly. Further details of the present exemplary system and method will be provided below,
  • orthopedic plate systems may be used in the treatment of various spinal conditions.
  • the plate portion of the orthopedic plate system when applied to stabilize the position of cervical vertebrae, is designed to lie near and posterior to the esophagus of the patient. Due to its relative location to the esophagus and other connective tissue, the top surface of the plate portion may be smooth and free of sharp corners to prevent irritation or piercing of the esophagus and surrounding tissue. Further, in order to prevent irritation and/or piercing, any connection hardware that is used to couple the plate portion to the cervical vertebrae should remain even with or below the top surface of the plate portion.
  • the present exemplary system and method provide an orthopedic plate system including a bone plate with thru-bores having varying diameters, with the larger diameter being constrained on the top and the bottom by smaller bore diameters. Further, a screw system is described below that, when assembled, is configured to leverage the varying bore diameter of the thru- bores formed in the bone plate to prevent the screw system from backing out.
  • the present exemplary system and method provides anti-back out protection with a minimal engagement surface on the bone plate. Consequently, the profile size of the bone plate, when compared to traditional orthopedic plate systems, is reduced. This reduction in profile size adds comfort to the patient by reducing the likelihood that difficulty in swallowing will develop due to the presence of the orthopedic plate system.
  • ring or “expansion ring” shall not be interpreted as necessitating a circular cross section. Rather, as used herein and in the appended claims, the term “ring” or “expansion ring” may include any object having a substantially closed periphery regardless of the cross-sectiona! profile.
  • the term “ring” or “expansion ring” shall include a split ring.
  • the term “ring” shall also include objects having flat sided profiles, curvilinear profiles, and/or profiles defined by a varying radius.
  • pin shall be interpreted broadly to include any elongate member, and is not limited to cylindrical elongate members.
  • pin shall apply to elongate members having a circular, a quadratic, and/or non- symmetric cross-sectional profile.
  • FIG. 1 illustrates an assembled cervical plate system (100), according to one exemplary embodiment.
  • the exemplary cervical plate system (100) includes a number of components including, but in no way limited to, a bone plate (110) and at least one screw assembly (120) coupled to the bone plate (110).
  • the screw assemblies (120) are configured to be securely coupled to a patient's bone(s) while securely coupling to the bone plate (110) to provide structural and positional stability while preventing issues with the screw assembly backing out.
  • the exemplary cervical plate system (100) when assembled, maintains the highest point of the screw assembly (120) below the highest surface of the bone plate (110).
  • FIG. 2 is an exploded view of the exemplary cervical plate system (100) illustrating the components of the screw assembly (120).
  • the screw assembly (120) includes, but is in no way limited to, a pull-lock pin (200), an expandable ring (210), and a bone screw (220).
  • the various portions of the screw assembly (120) are selectively inserted into the thru bore(s) (230) formed in the exemplary bone plate (110).
  • the exemplary cervical plate system (100) is able to maintain a relatively low profile while providing structural support and preventing screw back out.
  • a detailed description of each of the components of the exemplary cervical plate system (100) is provided below, followed by a description of their interaction during assembly.
  • FIGS. 3A 1 3B, and 3C illustrate various views of the bone plate (110), according to one exemplary embodiment.
  • the bone plate generally includes a main plate body (300) having a number of material cut-out(s) (310) and thru-bore(s) (230) formed therein.
  • the plate body (300) of the bone plate (110) is slightly curved to follow the shape of a spinal column and may be formed out of any number of biocompatible metals including, but in no way limited to, stainless steel, titanium, or a titanium alloy.
  • the construction of the plate body (300) may be made of non-metal materials including, but in no way limited to, carbon reinforced Polyetheretherketone (PEEK), and the like.
  • PEEK Polyetheretherketone
  • the plate body (300) has a beveled rounded periphery to eliminate any sharp or abrupt edges that could potentially be damaging to surrounding tissue.
  • the material cut-out(s) (310) formed in the plate body (300) may serve a number of purposes.
  • the material cut-out(s) (310) may be designed to eliminate superfluous material, thereby reducing the overall weight of the bone plate (110), while maintaining the desired structural integrity.
  • the various material cut-out(s) (310) may be configured to facilitate handling of the bone plate (110) during installation or removal with a tool such as, but in no way limited to, forceps. Further, the material cut-out(s) (310) may also provide functional access to tissue and/or bone located behind an installed bone plate (110) without necessitating removal of the plate.
  • FIG. 3C is a cross-sectional view detailing an exemplary varying profile of the thru-bore (230), according to one exemplary embodiment.
  • a plurality of thru-bores (230) are formed in the plate body (300), six in the exemplary embodiment illustrated in FIG. 3A.
  • a pair of thru-bores (230) are formed at each of the extreme ends and the center of the plate body (300), according to the exemplary embodiment illustrated in FIG. 3A.
  • any number of thru-bore configurations may be employed in the plate body (300) to accomplish varying desired coupling points.
  • each of the exemplary thru-bore(s) (230) include a reception chamfer (320) formed at the interface with the top surface of the plate body (300).
  • the reception chamfer (320) of the exemplary thru bore(s) (230) facilitates reception of a screw assembly (120; FIG. 2) while eliminating the formation of a sharp or potentially damaging edge at the surface of the plate body (300).
  • the thru-bore (230) includes a varying bore profile including a top reception diameter (330), a center cavity diameter (350), and an exit diameter (340) defined by a bore stop (360).
  • both the top reception diameter (330) and the exit diameter (340) of the exemplary thru- bore(s) (230) are smaller than the central cavity diameter (350).
  • a screw assembly (120; FIG. 2) having a selectively actuated expansion member may be inserted into the thru-bore(s) (230) and the expansion member actuated to approximately the diameter of the central cavity diameter (350).
  • expanding an expansion member such as an expandable ring (210) to approximately the diameter of the central cavity diameter (350) will create an interference fit between the plate body (300) and the expansion member in all directions, thereby eliminating any degrees of freedom the screw assembly (120; FIG. 2) may have relative to the plate body (300).
  • the expansion member may be actuated to a size slightly greater than that of the reception diameter (330) yet less than the central cavity diameter (350).
  • the size of the expansion member will prevent exit of the screw assembly (120; FIG. 1) from the thru-bore (320) while allowing for movement of the screw head within the thru-bore. This movement may be beneficial as an intermediate step when a surgeon is initially placing the bone plate.
  • the bore stop protrusion (360) that defines the exit diameter (340) of the thru-bore (230) may cause the exit diameter to be smaller than the diameter of the head base (415; FIG. 4) of the screw assembly (120). Consequently, the screw assembly (120) may be inserted into a bone via the bone plate (110) until the head base (415; FIG. 4) is seated upon the bore stop (360).
  • the incorporation of the bore stop provides for consistent insertion of the screw assembly (120) relative to the top surface of the bone plate (110). While the bore profile of the present exemplary thru-bore (230) is illustrated as having gradual changes in the internal diameter, abrupt or dramatic variations in profile of the thru-bore (230) may also define the thru-bore, according to one exemplary embodiment.
  • FIGS. 4A through 4D detail a number of elements of a bone screw (220), according to one exemplary embodiment.
  • the bone screw (220) includes features generally classified as a thread portion (400) and a head portion (410).
  • the thread portion (400) of the bone screw (220) is configured to be affixed to the bone of a patient during spine surgery.
  • the thread portion (400) of the exemplary bone screw (220) may include a self-tapping leading edge (450), as is best shown in FIG. 4B.
  • the incorporation of a self-tapping leading edge in the thread portion (400) of the bone screw (220) provides the bone screw with the ability to remove bone material as it is being inserted, eliminating a step of a surgeon drilling a pilot hole prior to insertion of the bone screw.
  • the head portion (410) of the bone screw (220) includes a number of functional features including, but in no way limited to, a plurality of driving features (420) formed on a head base (415), a ring channel (430) formed in a side of the driving features, and a pin bore (440) extending from the center of the head portion into the center of the thread portion (400).
  • the head portion (410) of the bone screw (410) transitions from the thread portion (400) with the head base (415).
  • the outer diameter of the head base (415) is larger than the outer diameter of any section of the thread portion (400).
  • the thread portion of the bone screw may pass through an appropriately sized thru-bore (230; FIG. 2) substantially corresponding in size with the thread portion while preventing the head base from passing there through. This configuration allows for consistent insertion depth of the bone screw (220) into a desired thru-bore (230; FIG. 2).
  • a number of protrusions in the form of driving features (420) are formed extending upwardly from the head base (415), according to one exemplary embodiment. As illustrated in FIGS. 4A and 4C 1 the shown embodiment includes three protrusions acting as driving features (420). However, any number of driving features (420) may be formed on the head base (415), according to the teachings of the present exemplary system and method. According to one exemplary embodiment, at least the upper portion of the driving features may be engaged by a corresponding driving feature during installation. According to this exemplary embodiment, the corresponding driving feature (not shown) may engage the driving features (420) and impart a rotational force thereon, driving the thread portion (400) of the bone screw (220) into a desired bone.
  • an annular groove is formed in the driving features (420) to form a ring channel (430) around the head portion (410) just above the head base (415).
  • the ring channel (430) formed in the driving features (420) of the present exemplary bone screw (220) is sufficiently deep to receive and house an expandable ring (210; FIG. 2) in a relaxed state and retain the expandable ring when driven open to retain the screw assembly (120; FIG. 1) in a thru-bore (230; FIG. 2).
  • a pin bore (440) is also formed in the exemplary bone screw (220), as is best illustrated in FIG. 4D.
  • the pin bore (440) is formed concentric with the axis of the bone screw (220) and has a diameter substantially similar to the diameter of the pull-lock pin (200; FIG. 2).
  • the pin bore (440) may correspond in height with a fraction of the height of a pull-lock pin (200; FIG. 2) to assure that a portion of the pull-lock pin is above the driving features (420) for grasping and pulling during operation.
  • FIGS. 5A and 5B illustrate the expandable ring (210) of the screw assembly (210; FIG. 2), according to one exemplary embodiment.
  • the exemplary expandable ring is configured to mate with and be selectively expanded in the ring channel (430; FIG. 4A) of the bone screw (220).
  • the expandable ring (210) includes a substantially circular outer rib (500).
  • the substantially circular outer rib is free of gaps or splits.
  • the circular outer rib may include an expansion gap (505) formed therein.
  • the width of the outer rib (500) is defined by the difference between the inner diameter (530) of the outer rib and the outer diameter (540) of the outer rib.
  • the difference between the inner diameter (530) and the outer diameter (540) is such that the expandable ring (210) may be retained in the ring channel (430; FIG. 4A) of the bone screw (220; FIG. 2) in both an un-expanded state and an expanded state within a thru-bore (230; FIG. 2).
  • the expandable ring (210) includes a number of expansion ribs (510) protruding from the outer rib (500) toward the center of the expandable ring.
  • the expansion ribs (510) terminate in a lock pin engagement surface (515) and define a driving feature orifice (520) between each pair of adjacent expansion ribs and a pin orifice (530) between the lock pin engagement surfaces.
  • the driving feature orifices (520) are configured to receive the driving features (420; FIG. 4C) formed on the head portion (410; FIG. 4A) of the bone screw (220; FIG. 2), during assembly.
  • the lock pin engagement surfaces (515) cause the pin orifice (530) to be concentrically aligned with the pin bore (440; FIG. 4D) when assembled.
  • the engagement surfaces are configured to receive a pull-lock pin (200; FIG. 2) and translate any variations in the surface profile of the pull- lock pin to the outer rib (500) as the pull-lock pin is pulled from the pin bore (440; FIG. 4D), thereby controlling the expansion and/or contraction of the outer rib (500).
  • the expandable ring (210) having a constant outer ring (500) will elastically or plastically bend around the areas where the expansion ribs (510) are coupled to the outer ring (500) as the pull-lock pin is pulled from the pin bore (440; FIG. 4D).
  • FIG. 6 illustrates an exemplary pull-lock pin (200) according to one exemplary embodiment.
  • the exemplary pull-lock pin (200) is a substantially cylindrical member having a proximal (670) and a distal end (675). Additionally, a number of cut outs and/or tapers are formed in the pull- lock pin (200) to create a varying outer pin diameter.
  • the pull-lock pin (200) includes a pull element (600) that will be exposed from the top of the bone screw (220; FIG. 2) when assembled. The pull element (200) tapers into a break taper (610) that forms the smallest diameter of the pull-lock pin (200).
  • the break taper (610) is configured to yield when a desired friction is imparted on the expandable ring (210; FIG. 2). Additionally, when assembled, the break taper (610) engages the expandable ring (210; FIG. 2), allowing the expandable ring to be in a relaxed state.
  • an engagement taper (620) is formed adjacent to the break taper (610), leading to a lock surface (640).
  • the engagement taper (620) is a graduated surface configured to facilitate initial alignment and engagement of the pull-lock pin (200) with the pin orifice (530; FIG. 5A) of the expandable ring (210; FIG. 5A).
  • the engagement taper (620) and the lock surface (640) are separated by a retention lip (645). More particularly, according to one exemplary embodiment, the retention lip (645) has an outer diameter that is greater than the lock surface (640). Furthermore, the retention lip is formed at a substantially perpendicular angle to the lock surface (640). Consequently, when an expandable ring (210; FIG. 5A) engages the lock surface (640), the ring is unable to recede back to the engagement taper (620).
  • the lock surface (640) defines an engagement diameter of the pull-lock pin (200).
  • the lock surface (640) has a diameter substantially corresponding to the pin orifice (530; FIG. 5A) in an expanded ring state.
  • the lock surface (640) has a substantially constant diameter.
  • any number of graduated surfaces may also define the lock surface.
  • the pull-lock pin (200) is pulled from the pin bore (440; FIG. 4D) such that the lock pin engagement surfaces (515; FIG. 5A) of the expandable ring (210) engage the lock surface (640) to expand the expandable ring to an appropriate diameter within the thru-bore (230; FIG. 2).
  • the outer pin diameter of the lock surface (640) is sufficient to expand the expandable ring (210; FIG. 2) to a desired friction inducing state, while still constraining the expandable ring in the ring channel (430; FIG. 4A) and without permanently deforming the expansion ring. Additionally, when the pull stop (650) engages the expandable ring, translation of the pull-lock pin (200) will be impeded, increasing the force exerted on the pin (200), causing the pin to yield at the break taper (610). Further detail of the function and operation of the exemplary cervical plate system (100) will be described below with reference to FIGS. 7-12B.
  • FIG. 7 illustrates a method for installing the exemplary cervical plate system (100; FIG. 1), according to one exemplary embodiment.
  • the present exemplary method for installing the cervical plate system (100; FIG. 1) includes placing the bone plate adjacent to one or more desired vertebral bones (step 700). Once the bone plate is appropriately positioned, the screw assembly may then be presented to a thru-bore of the bone plate with the expandable ring in a relaxed state at a small diameter (step 710). The screw assembly is then driven through the thru-bore in the bone plate into the desired vertebral bone (step 720) until the enlarged head of the screw assembly is within the central cavity of the thru- bore, seated on the bore stop (step 730).
  • the pull-lock pin may be pulled to enlarge the diameter of the expandable ring, thereby capturing the screw assembly within the thru- bore (step 740). Further details of each step of the present exemplary method will be provided below with reference to FIGS. 8 through 11.
  • the first step of the exemplary method is to place the plate adjacent to a desired vertebral bone (step 700).
  • the placement of the bone plate (110; FIG. 1) relative to a vertebral bone in a patient may be pre-operatively determined based on a pre-operative examination of the patient's spinal system using non-invasive imaging techniques known in the art, such as x-ray imaging, magnetic resonance imaging (MRI), and/or fluoroscopy imaging, for example. Any additional preparation or work may be done on and around the desired vertebral bone prior to positionally orienting the bone plate.
  • the bone plate (110) is oriented such that the reception chamfer (320) is facing away from the desired bone (800), facilitating insertion of the present screw assembly.
  • the screw assembly may be presented to a thru-bore of the bone plate with the expandable ring in a relaxed state (step 710).
  • the screw assembly (120) may be delivered to the surgeon as single three piece assembly including the bone screw (220), the expandable ring (210), and the pull-lock pin (200).
  • the pull-lock pin (200) when delivered to the surgeon, the pull-lock pin (200) is undeployed and the expandable ring (210) is in a relaxed state. More specifically, according to one exemplary embodiment, the break taper (610; FIG. 6) of the pull-lock pin (200) is engaged with the pull-lock pin engagement surfaces (515; FIG.
  • the screw assembly (120) may then be driven through the thru-bore (230) in the bone plate (110) into a desired vertebral bone (step 720), as illustrated in FIG. 9B.
  • the screw assembly (120) may be driven into the desired vertebral bone by coupling a driving tool to the driving features (420) of the bone screw (220).
  • the driving tool may impart a rotational force on the head portion (410) of the bone screw (220). Consequently, the self-tapping thread portion (400; FIG. 4A) of the bone screw (220) will remove bone material as it advances into the desired bone.
  • the screw assembly (120) may be partially driven initially if multiple screw assemblies (120) are to be inserted in a single bone plate (110) or if further work is to be done by a surgeon prior to final assembly.
  • the screw assembly (120) may be driven through the thru- bore (230) until the head portion (410) of the bone screw (220) is within the central cavity of the thru-bore (step 730), as shown in FIGS. 10A and 10B.
  • consistent seating of the screw assembly (120) in the thru-bore (230) may be accomplished by driving the bone screw (220) into the thru-bore (230) until the head base (415; FIG. 4A) of the bone screw seats upon the bore stop (360; FIG. 3C) within the thru-bore.
  • FIGS. 10A and 10B illustrate a screw assembly (120) seated in the thru-bore (230) as described above.
  • the pull-lock pin (200) may be engaged to enlarge the diameter of the expandable ring (210), capturing the screw within the thru-bore (step 740), as illustrated in FIGS. 11A and 11 B.
  • the pull-lock pin (200) is engaged by applying a pulling force (F1) to the pull element (600) of the pull-lock pin (200).
  • the expansion ring (210) is acted upon by the varying profile of the pull-lock pin (200).
  • the upward pulling force (F1) causes the pull-lock pin (200) to translate proxirnally from the pin bore (440), resulting in the engagement taper surface (620) of the pull-lock pin (200) imparting an outward force (F2) on the expansion ring (210).
  • the increasing diameter of the engagement taper surface (620) imparts an increasing force on the expansion ring (210) until the lock surface (640) of the pull-Jock pin is engaged and imparting a desired outward force (F2) upon the expansion ring.
  • pull-lock pin (200) imparts a radial force on the expansion ring (210) of the exemplary embodiment detailed herein
  • movement of the pull-lock pin is in no way limited to an axial translation.
  • a pull-lock pin (200) having a non- circular cross-sectional profile, such as a triangle or other lobed profile may be rotated within the pin bore (440) to impart a changing radial force on the expansion ring (210).
  • the diameter of the expansion ring is enlarged about the head portion (410; FIG. 4A) of the bone screw assembly (120).
  • the enlarging of the expansion ring (210) about the head portion (410; FIG. 4A) of the bone screw assembly (120) imparts an outward force (F2) from the expansion ring to the inner surface of the thru-bore (230).
  • the outward force (F2) exerted by the expansion ring (210) to the thru-bore (230) creates a frictional fit that captures the bone screw (220) within the thru-bore of the bone plate.
  • the outer diameter of the expansion ring (210) in its expanded state is larger than both the reception diameter (330; FIG. 3C) and the exit diameter (340; FIG. 3C) of the exemplary thru-bore (230). Consequently, the bone screw assembly (120) is prevented from backing out from, or further advancing in the thru-bore (230).
  • the pull element (600) of the pull-lock pin may fracture from the remaining portion of the pull-lock pin (200) at the break taper (610), similar to the operation of a pop-rivet pin. More particularly, according to one exemplary embodiment, as the pulling force (F1) is continually applied to the pull element (600), the pull-lock pin (200) will continue to translate proximally. Consequently, the lock surface (640) will translate against the edge of the expansion ring (210) until the larger diameter of the pull stop (650) comes in contact with a distal surface (212) of the expansion ring.
  • FIGS. 12A and 12B illustrate the present exemplary system in a locked state.
  • the remaining portion of the break taper (610) is the most proximal remaining portion of the pull-lock pin (200).
  • the dimensions of the pull-lock pin (200) relative to the height of the head portion (410) of the screw assures that no portion of the pull-lock pin (200) remains above the top of the bone plate (110; FIG. 1).
  • the lock surface (640) is engaged with the inner portion of the expansion ring (210)
  • the desired outward force (F2) is maintained, thereby locking the single bone plate (110) to the screw assembly (120).
  • back-out of the screw assembly (120) is prevented.
  • the present exemplary orthopedic plate system (100; FIG. 1) has been described, for ease of explanation only, in the context of a cervical plate system, the present exemplary systems and methods may be applied to any number of orthopedic fixtures.
  • the present bone screw assembly (120) may be used to couple any number of orthopedic apparatuses to a desired bone, for any number of purposes, as long as the connecting orthopedic apparatus includes a thru-bore substantially conforming with the configurations described herein.
  • the present exemplary systems and methods provide for coupling an orthopedic plate to one or more bones while preventing back-out of the fastener.
  • the present exemplary system is configured to leverage the varying bore diameter of a thru-bore formed in the bone plate to prevent the screw system from backing out while utilizing a minimal engagement surface on the bone plate. Consequently, the profile size of the bone plate, when compared to traditional orthopedic plate systems, is reduced and the dangers associated with screw back-out are reduced. This reduction in profile size adds comfort to the patient by reducing the likelihood that difficulty in swallowing will develop due to the presence of the orthopedic plate system.

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  • Health & Medical Sciences (AREA)
  • Orthopedic Medicine & Surgery (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Surgery (AREA)
  • Neurology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Medical Informatics (AREA)
  • Molecular Biology (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Surgical Instruments (AREA)
  • Prostheses (AREA)

Abstract

La présente invention concerne un dispositif orthopédique (100) comprenant un élément implantable (110) traversé d'un perçage (230) caractérisé par un diamètre à l'entrée (330), un diamètre intermédiaire (250) et un diamètre en sortie (240). Selon un mode de réalisation, le diamètre intermédiaire (250) du perçage traversant (230) est supérieur aussi bien au diamètre en entrée (330) qu'au diamètre en sortie (240). En outre, le dispositif orthopédique (100) comporte un ensemble à vis (120) configuré pour se coupler au perçage traversant (230) et comprenant un segment fileté (400) et une tête sélectivement expansible (410). Cette tête sélectivement expansible (410) est constituée d'une bague expansible (210) et d'une goupille de verrouillage arrachable (200) configurée pour déployer sélectivement la bague expansible (210) lorsqu'on arrache dudit ensemble à vis (120) la goupille de verrouillage (200).
PCT/US2007/007014 2006-03-21 2007-03-21 Mécanisme de verrouillage cervical à rivet aveugle WO2007109316A2 (fr)

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US20070225717A1 (en) 2007-09-27
WO2007109316A3 (fr) 2008-04-24
US20140309704A1 (en) 2014-10-16
US9125705B2 (en) 2015-09-08
US8728128B2 (en) 2014-05-20

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